In general, a person who is hearing impaired and who uses a conventional hearing aid can use a telephone handset in one of two modes. In one mode of operation, they use the telephone handset in a conventional manner, allowing the acoustic sound waves emitted by the handset's speaker (also referred to as a receiver) to be picked up by the hearing aid's microphone in the same way that the hearing aid's microphone would pick up the sound of an external source (e.g., another person in the same room). The hearing aid then converts the acoustic sound waves to an electrical signal that is processed prior to being converted back to sound waves and broadcast to the user via the hearing aid's speaker (also referred to as a receiver). In the second mode of operation, the hearing aid uses an electromagnetic induction coil to pick up an electromagnetic signal that corresponds to the acoustic sound waves produced by the telephone handset. The induction coil, which is typically integrated within the hearing aid, generates an electrical signal that is then processed by the hearing aid and converted to acoustic sound waves that are broadcast to the user. The hearing aid may include means for the user to select which mode of operation they prefer, acoustic or electromagnetic.
In recent years, a number of companies have undertaken efforts to improve upon the quality, performance and usability of telephone coupled hearing aids. In general, these efforts have been directed at four specific areas. First, various methods have been proposed to increase the strength of the electromagnetic signal produced by the handset. Many of these methods use a secondary flux coil, both as a means of increasing the electromagnetic signal and as a means of providing additional mounting flexibility. Second, a number of techniques have been used to improve upon the sensitivity of the induction coil that is integrated into the hearing aid. Third, improvements in signal processing, for example the use of multi-band digital signal processors, continue to improve upon the overall quality of the sound produced by the hearing aid. Fourth, a number of user convenience features such as automated mode switching have provided hearing aid users with a more user-friendly device.
Although a number of developments have been made that improve the sound quality and coupling efficiency of a hearing aid when used with a telephone handset, many users still find the performance inadequate. As a result, many people with hearing disabilities are unable, or unwilling, to use a conventional telephone. Accordingly, what is needed in the art is a telephone that can provide a hearing disabled person with improved performance when electromagnetically coupled to their hearing aid. The present invention provides such a system.